THE SPONGES OF THE WEST-CENTRAL PACIFIC 31 



but was scattered around other sides of the island, too. In Truk, it was 

 moderately common, and in the Palaus very common. 



This species is usually ramose, but some of the Palau specimens were 

 lamellate, or wall-shaped. Heights of at least 30 cm are reached, particularly 

 in the Ebon specimens. The diameters of the branches are usually about 

 2 cm, but some are as narrow as only 1 cm. The lamellate specimens were 

 thicker, up to 4 cm. 



In general, the color was black but varied toward gray in the portions 

 of specimens which were most shaded. An outstanding exception is the 

 matter of all the specimens from Ebon. Throughout that atoll this species 

 was consistently brown, rather than black; but in Ebon, as everywhere else, 

 the endosome was the same drab shade. There was no distinctive odor to 

 this sponge, such as characterizes Ircinia and some Spongias. The con- 

 sistency was spongy, and it was easily cut. 



The surface is conulose; and from each conule, numerous conspicuous 

 lines radiate, so that the pattern is one of stars or stellate units. The conules 

 are from 1 to 2 mm high and 2 to 4 mm apart. The common distance apart 

 is 3 mm. The pores vary in diameter from 40 jx to 110 /y. but are usually 

 between 50 p. and 80 jx. They are distributed in groups within the meshes 

 of the dermal skeleton, which is to be discussed below. The oscules in speci- 

 mens actually vary from 1 to 11 mm in diameter, but in life they are rarely as 

 much as 4 mm and seldom as little as 2 mm in diameter. They are scattered 

 in all sorts of places, are not particularly terminal, are often as numerous 

 as only 3 cm apart, but occasionally may be practically absent. 



The ectosome of this species was carefully studied, because of the diffi- 

 culty of locating it between Thorecta and Thorectopsamma. There is a very 

 definite dermal reticulation of fibers, which are much like those of the endo- 

 some but in size are intermediate between those referred to as principal fibers 

 and the others termed secondary fibers. That is to say, those of the dermis 

 are about 100 fx in diameter and the outline meshes are about 300 /a to 600 jx 

 in diameter. These meshes are filled in by a thin dermis scarcely 15 fx thick 

 and perforated by the pores. In the majority of specimens, this dermis con- 

 tains no foreign material ; but, particularly in the specimens from Ponape, 

 Truk, and the Palaus, there are scattered bits of sand or other debris in it — 

 not enough, however, to warrant calling it a sand-filled cortex. 



The endosome is filled with a macroscopic fibro-reticulation. Among 

 the meshes of this occur very dense protoplasmic structures M'hich are 

 crowded with small spherical flagellate chambers. These vary from 20 /x to 

 35 [x in diameter but the vast majority of them are between 25 /x and 30 [x 

 in diameter. 



The skeleton comprises fibers roughly separated into two sizes; the 

 larger or principal ones are commonly about 200 fx in diameter but vary from 

 150 fx to 250 jx. These always contain much foreign material and, in some 



